The present invention relates to a motorcycle oil pump, and in particular, to an oil pump having intermeshing gears with an improved tooth design that provides improved flow over the prior art.
Internal combustion engines such as those for motorcycles typically have an oil pump that is a dry sump-type system with two sets of intermeshing external rotary gears. The gears are typically driven on a common drive shaft with one gear set supplying pressurized oil to the engine for lubrication, with the other gear set scavenging excess oil from the crankcase to the oil tank. Oftentimes, the oil pump does not provide sufficient oil for the engine, especially through certain RPM ranges. In other applications, performance modifications may be made to the engine that require increased oil flow to provide proper lubrication as the stock oil pump does not have sufficient capacity.
In order to accommodate increased oil flow, a simple solution is to provide a larger capacity oil pump. However, a larger capacity pump requires additional space that may not be available and prevents retrofitting to an existing engine. Therefore, it is desirable to utilize an oil pump having the same space requirements as a stock pump. It is also desirable to mount to the existing drive shaft to minimize the modifications required to mount to the engine. If an existing oil pump is used, one modification that provides increased flow is to widen the gear sets or increase the depth of the gears. However, clearance constraints may prohibit widening of the gears or may limit the depth of the gears. Another solution is to increase the angular velocity of the gears. This method of providing increased flow is undesirable as it may increase the wear of the current pump and require more maintenance. It also requires increasing the angular velocity of the drive shaft or adding a gear intermediate the drive shaft and the pump gears.
Another alternative is to change the gear profile. A typical stock oil pump gear includes fourteen teeth, as shown in FIG. 1. An improved gear tooth profile may provide for pumping a larger volume of oil and maintaining a higher oil pressure, overcoming the pressure problems associated with some engines. An improved gear tooth profile could provide for utilizing gears that may replace the stock gears and provide improved flow with an identical outer radius and RPM.
Another problem with existing oil pumps is that the ratio between oil supply volume and oil return volume is not optimized. Under some operating conditions, the engine may be overwhelmed by oil. The crankcase then becomes filled, resulting in oil carryover, wherein excessive oil is blown out of the crankcase breather.
It can be seen that a new pump is needed that provides improved flow over existing designs. Such an oil pump should provide increased oil flow without requiring additional space for the oil pump. Such a design should provide for retrofitting existing oil pumps with an improved gear tooth profile, resulting in increased oil pumping volume. Such a system should provide for optimization of the pump flow for the supply as well as the pump flow ratio between the supply and the return. The present invention addresses these as well as other problems related to oil pumps for internal combustion engines.
The present invention is directed to a dry sump type oil pump system that utilizes intermeshing spur gears having an improved tooth profile for improved pumping and volume.
A motorcycle engine oil pump includes a pump body and a cover. The pump body includes two sets of gears, intermeshing supply gears and intermeshing return gears. The gears are spur gears having nine teeth with an improved involute tooth profile. The profile of the gears and greater intermeshing provide improved flow over the prior art. The present invention provides for retrofitting to existing engines as the gears can be fitted in a body and cover having the same outer dimensions. The gear chambers are modified slightly to accommodate the different distance between the gear centers due to the greater tooth overlap from greater intermeshing. However, the driven supply gear and return gear are coaxial with the existing drive shaft to provide for retrofitting. In addition, the depth of the supply gears and return gears is increased over the prior art so that improved flow is achieved without greater angular velocity and without a greater diameter.
The oil pump also includes various passages for directing oil to the various components to be lubricated and for reclaiming oil from the oil tank and sump. The oil pump also includes a check valve and a pressure relief valve that are set to accommodate the increased flow over the prior art. With the optimized placement of various passages and levels, as pressure increases and the plunger of the relief valve and ball of the check valve are moved, oil is directed to different components at the various pressures, thereby providing lubrication to components as the need arises.
With the improved gear design, pump volume for the supply gears is increased by thirty eight percent over a comparable pump of the prior art while the return gears increase pump volume by sixty one percent as compared to the prior art. This is achieved without increasing gear angular velocity, gear diameter, or the width of the pump body and cover assembly and utilizing existing geometry that are compatible with existing engines.
These features of novelty and various other advantages that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.